A pesticide is a bioactive material which destroys or inhibits the action of plant or animal pests. The general term pesticide includes insecticides, herbicides, fungicides, plant growth regulators, rodenticides and miticides.
Pesticides are widely used in soil and foliar applied to desired plants, such as ornamentals, plants grown for food and fiber and turf, for the control of weeds, insects and disease. Typically, pesticides are formulated into conventional forms such as dusts, granules, wettable powders and emulsions using techniques well known in the art. A preferred means of applying pesticides for both consumers and professional applicators is dry granules for use in the broadcast delivery of the pesticides.
Granular pesticides are important commercial products because of their ability to eliminate undesirable vegetation, diseases, insects and the like and their ease of application, either by hand or a mechanical means. The granular pesticide can be a pesticide applied to an inert material, like clay or ground corn cobs, or can be a combination fertilizer/pesticide, wherein the pesticide is applied to a fertilizer material.
In a granular form, a pesticide is impregnated into or absorbed onto an inert material or a fertilizer material. The granular pesticide product is applied to soil and/or vegetation by directly spreading pesticide granules onto the soil and/or vegetation at a suitable dosage rate.
The dry granules of the present invention are those granules which can be applied with a dry spreader or by hand to a target area and when exposed to water by way of, for example, rain or irrigation, will allow the pesticide material to migrate further away from the carrier. The granules of the present invention include inert carriers that do not disintegrate readily upon watering. In order to facilitate the spreading of the pesticide, granules of the present invention may also be prepared so as to readily disintegrate when exposed to water and spread thus increasing the area affected by the pesticide. These granules are often prepared from wood dust, diatomaceous earth compositions or mineral components, such as limestone or dolomite, and may contain surfactants and/or binders to aid in the disintegration and dispersion of the granules upon exposure to water. Granules for delivering pesticides also include fertilizers impregnated with a pesticide.
Microemulsions, another conventional formulation for active chemical agents, are a subclass of emulsions and are a thermodynamically stable dispersion of one liquid phase into another, stabilized by an interfacial film or surfactant. Microemulsions are typically clear solutions and contain emulsion droplets having an average particle size of about 0.01 to 0.1 microns. These formulations typically contain an oil phase comprising at least one pesticidally active ingredient and emulsifiers. Substantially water-insoluble pesticides that are liquid at room temperatures can be dispersed as they are in water. When the active ingredients are solid or of high viscosity, water immiscible organic solvents may be used to dissolve them. Typically, the amount of emulsifiers needed in a microemulsion is higher than that in an emulsion. Microemulsifiable concentrates contain high levels of active ingredients and emulsifier and upon dilution in water form compositions containing emulsion droplets having an average particle size of about 0.01 to 0.1 microns. One or more emulsifiers may be used in preparing the microemulsifiable concentrates of the present invention. The concentrates can comprise a single surfactant, for example, a non-ionic surfactant such as a condensation product of castor oil and a polyC2-4alkylene oxide. Combinations of strongly hydrophobic non-ionic surfactants (preferably those having a hydrophilic-lipophilic balance (HLB)>13) and hydrophobic anionic surfactants are also preferred emulsifiers for microemulsions and microemulsifiable concentrates.
Microemulsions and microemulsifiable concentrates are well known in the art as shown by, for example, European Patent Application No. EP 160 182 A2; U.S. Pat. Nos. 4,870,103; 4,904,695; 4,954,338; 4,973,352; 5,242,907; 5,317,042; 5,326,789; 5,334,585; U.S. Patent Application Publication Nos. 2003/087764, 2004/0132621 and 2005/0043182; PCT Publications WO 99/65300 and WO 02/45507.
The granular pesticides of the present invention comprise a pesticide or mixture of pesticides blended in, absorbed, impregnated or coated onto a solid substrate. The solid substrate can be an inert material, for example, clay, and/or a fertilizer material, for example, urea/formaldehyde, potassium chloride, ammonium compounds, phosphorus compounds, sulfur, similar plant nutrients and micronutrients, and mixtures and combinations thereof, both synthetic and naturally occurring organic and inorganic materials.
An important function of a broadcast granule formulation includes the release and coverage of the active chemical agent(s) to the surrounding soil after application of the granule. Two mechanisms for releasing active chemical agent(s) contained in or on the granule carrier is: (1) abrasion of the pesticidally active material from the carrier, or alternatively, (2) the granular carrier disintegrates leaving the pesticidally active material in close proximity of the granule origin. In the aforementioned mechanisms, the pesticidally active material is moved away from the granule locus by the dynamic force of water passing the granule locus. A disadvantage to these mechanisms is that the pesticidally active materials that are substantially water-insoluble do not readily associate with the passing water.
A common problem associated with known granules is the inability of the active chemical agent(s) to leave the granule. The inability to leave the carrier is common when the active chemical agent(s) absorbs too deeply into the inert carrier, or the active chemical agent(s) is too tightly adhered to the inert carrier.
Known methods of increasing the coverage of a pesticidally active material to the area surrounding the granule include the use of a dispersable granule that breaks down upon exposure to water to cover a greater surface area, thereby improving distribution of the active chemical agent(s) over a specified area. While these granules improve the area of the active chemical agent coverage, it does not increase the ability of the active chemical agent to migrate further from the outer boundary of the granular carrier. Examples of dry spreadable granules are provided in U.S. Pat. Nos. 6,231,660; 6,375,969; 6,416,775 and 6,613,138.
It would be advantageous to create a granular formulation containing a pesticidally active material that would readily associate with migrating water, thereby increasing the coverage of the pesticidally active material in the soil. The present invention combines the known formulation methods of microemulsions and dry broadcast granules to accomplish this goal.